1. Technical Field
The present invention relates to a laser irradiating method and a device for the method, and more particularly, to a laser irradiating method of condensing or focusing a laser beam from a laser oscillator through a lens, and irradiating an object to be irradiated which is mounted on a stage with the laser beam to reform the object to be irradiated, and a device for the method, which have a mirror for maintaining a temperature of the lens and also a focal distance.
2. Description of the Related Art
Up to now, in manufacture of crystallized silicon of a thin film transistor, an object to be irradiated having a thin a-Si (amorphous silicon) film formed on a glass substrate is irradiated with a laser beam, and the a-Si film is crystallized to provide a p-Si (polysilicon) film. As one of methods of irradiating the a-Si film with a laser beam to reform the a-Si film, there is a method in which a laser beam having a uniform intensity is applied to a mask, and the laser beam is then projected and focused on the a-Si film of the object to be irradiated by means of a condenser lens of an optical device. Thus, the object is irradiated with the laser beam (see for example, JP 3204986 B).
In the method, a laser beam that is produced by a laser oscillator that generates an excimer laser beam is introduced into the optical device, and appropriately diverted by means of a reflective mirror, and the intensity of the laser beam is equalized. After that, the laser beam is allowed to pass through the mask and the condenser lens so as to be shaped in a square line beam (pulse laser beam), and then condensed and transferred to the object to be irradiated. The object to be irradiated is located within a vacuum chamber of a laser beam anneal device.